fetch and interactive packages

There seems to be an inconsistency in the fetching of distfiles for
packages marked 'interactive fetch' and those that are not. Normally,
the fetching process will honor a set of alternative distfile
locations through the ${DIST_PATH} variable. However, for packages
marked 'interactive fetch' the distfile _must_ be located within
${DISTDIR} as per the following line in mk/fetch/fetch.mk:
${DISTDIR}/${_file_}: fetch-check-interactive do-fetch-file error-check
This prevents the possibility of placing the distfiles for
'interactive fetch' packages in an appropriate part of ${DIST_PATH}.
I am noticing this because I have some packages for proprietary
software that requires special downloading. Of course, those
distfiles should not be intermingled with the redistributable ones in
${DISTDIR}. Under the current system, it is impossible to have both
'interactive fetch' marked and a special location for this type of
distfile.
I'm not certain what make magic to suggest, but it seems that making
the above line somehow check all the components of ${DIST_PATH} (if
set) would be appropriate.
Thoughts?
Cheers,
Brook